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typefind: Make the flac check more tight to not mistace some aac files for flac. Fixes #570356.

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Add comments about the flac format. Tighten the check to not allow values that
refer to headers.
This commit is contained in:
Stefan Kost 2009-02-03 15:26:08 +02:00
parent 314d852e48
commit 080493ccff
1 changed files with 21 additions and 4 deletions
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25
gst/typefind/gsttypefindfunctions.c
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@ -567,14 +567,17 @@ flac_type_find (GstTypeFind * tf, gpointer unused)
}
}
/* flac without headers */
/* flac without headers (subset format) */
/* 64K should be enough */
while (c.offset < (64 * 1024)) {
if (G_UNLIKELY (!data_scan_ctx_ensure_data (tf, &c, 4)))
break;
/* look for frame header,
* http://flac.sourceforge.net/format.html#frame_header
*/
if (data[0] == 0xff && (data[1] >> 2) == 0x3e) {
/* bit 15 must be 0 */
/* bit 15 in the header must be 0 */
if (((data[1] >> 1) & 0x01) == 0x01)
goto advance;
@ -585,19 +588,32 @@ flac_type_find (GstTypeFind * tf, gpointer unused)
/* samplerate must be != 0x0f */
if ((data[2] & 0x0f) == 0x0f)
goto advance;
/* also 0 is invalid, as it means get the info from the header and we
* don't have headers if we are here */
if ((data[2] & 0x0f) == 0x00)
goto advance;
/* channel assignment must be < 11 */
if ((data[3] >> 4) >= 11)
goto advance;
/* sample size must be != 0x07 */
/* sample size must be != 0x07 and != 0x05 */
if (((data[3] >> 1) & 0x07) == 0x07)
goto advance;
if (((data[3] >> 1) & 0x07) == 0x05)
goto advance;
/* also 0 is invalid, as it means get the info from the header and we
* don't have headers if we are here */
if (((data[3] >> 1) & 0x07) == 0x00)
goto advance;
/* next bit must be 0 */
if ((data[3] & 0x01) == 0x01)
goto advance;
/* FIXME: shouldn't we include the crc check ? */
GST_DEBUG ("Found flac without headers at %d", (gint) c.offset);
gst_type_find_suggest (tf, GST_TYPE_FIND_LIKELY, FLAC_CAPS);
return;
}
@ -1149,7 +1165,8 @@ ac3_type_find (GstTypeFind * tf, gpointer unused)
/* can only be detected by using the extension, in which case we use the default
* GSM properties */
static GstStaticCaps gsm_caps = GST_STATIC_CAPS ("audio/x-gsm, rate=8000, channels=1");
static GstStaticCaps gsm_caps =
GST_STATIC_CAPS ("audio/x-gsm, rate=8000, channels=1");
#define GSM_CAPS (gst_static_caps_get(&gsm_caps))